USB: driver.c: remove err() usage

err() was a very old USB-specific macro that I thought had
gone away.  This patch removes it from being used in the
driver and uses dev_err() instead.

CC: Markus Grabner <grabner@icg.tugraz.at>
CC: Stefan Hajnoczi <stefanha@gmail.com>
CC: Julia Lawall <julia@diku.dk>
CC: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>